For a reference point if playing on PC you might consider using a Windows Mixed Reality Headset. I have most things at max (supersampling 1.8 I think) and get smooth VR. Could be my video card but doubt it. Guessing that Windows MR headsets are just more hooked into the OS than rift. Anyways, here are my pc stats: 8gb ddr3200, i5-8600k (new cpu that just came out), Radeon Vega 64. I wish I could give you fps but don't know how to measure that with WMR headset and pcars2 but it's plenty smooth.
In Assetto Corsa as a reference I'm getting 55+ fps in most cases with most everything maxed (reflection update on low).
Just mention this for anyone building a new vr setup consider the WMR headsets as they are cheaper, higher resolution than occulus, and I believe likely more efficient (not that Occulus probably can't fix that). I don't have any hard evidence, just drawing that conclusion based on what I see Occulus people writing about their results. Dont' see too many using the Vega 64 though so might be that making the difference, dunno.